Method of making ply board



Aug. 18, 1936. J. v. BAUER METHOD OF IAKING PLY BOARD Filed June 17, 1936 INVENTORL- cfaz'figz ,Faaer, fi- M146 Mammal s.

Patented Aug. 18, 1936 UNITED STATES PATENT OFFICE.

METHOD OF MAKING PLY BOARD Jordan V. Bauer, Chicago, 111., assignor to Stein,

Hall Manufacturing Company, Chicago, 111., a corporation of Delaware Application June 11, use, Serial in. sans;

13 Claims. (01. 154-33) .board is a continuous two step operation. It

consists of corrugating a strip of paper by means of heated fluted rolls, applying an adhesive to the tips of the corrugations on one side, bringing a liner in contact with it and forming the bond with the assistance of heat and considerable pressure. This operation may be considered as the first step and forms what is known as a. single faced corrugated board, comprising a corrugated strip of paper bonded to a smooth surfaced strip. The second step of the operation consists of applying an adhesive to the tips of the exposed corrugated surface, bringing a liner in contact with it and forming the bond with the assistance of heat and just sufilcient pressure to hold the paper surfaces in contact. The result of these two operations is a stifi paper board comprising two smooth outer paper surfaces bonded to an inner core of corrugated paper.

In the mhnufacture of double faced corrugated board, the adhesive problem is considerably more difllcult than that of adhesively combining two or more smooth surfaced strips of paper. In bonding two or more smooth surfaced strips of paper together in a continuous process, it is possible to apply any desired amount of pressure by means of rolls in order to assist the rapid formation of a bond. In the case of corrugated board, however, only a very small amount of pressure can be used to assist the formation of a bond between the single faced board and the second liner because of the danger of crushing the corrugation. As a result, points of poor contact develop where the corrugation tips do not touch the liner. It thus becomes necessary to apply a sufficient amount of adhesive to the tips of the corrugations so that there will be sufilcient adhesive present to completely fill in any points of poor contact between the liner and corrugation tips. In order to compensate for these adverse conditions, it is customarily necessary in using silicate of soda adhesive to heat the board after the second liner has been brought into contact. The heating tends to dry the adhesive and make it set more rapidly. The heating period is relatively short, however, for the liminating machines operate at a high rate of speed, for example, between and 325 feet of paper board per minute.

Because of these adhesive problems in connection with the manufacture of corrugated paper board, it is necessary that the adhesive used must be capable of a rapid increase in viscosity on the application of heat. when the board passes from the machine the adhesive must be sufficiently setup to hold the bonded surfaces together and allow the board to be cut and otherwise handled. Up to the present time the only adhesive that possesses this characteristic to a satisfactory degree and is also of low cost is the silicate of soda type. This is true to the extent that practically all of the present day machines for making corrugated paper board have been designed and built with the idea of using silicate of soda as the adhesive.

In the manufacture of corrugated paper board, it is not essential that the adhesive used should form a bond of extremely high agglutinant strength inasmuch as it is only n that the bond be slightly stronger than the paper itself. The essential feature necessary in an adhesive for double faced corrugated paper board is the ability to rapidly form a bond between two paper surfaces under conditions of heat and low pressure and possible 'poor contact between the surfaces.

Gelatinized starches or stach derivatives such as dextrine have previously been used as adhesives but have not been found satisfactory. The reason for the superiority of silicate of soda over such starch adhesives for use with laminated paper such as corrugatedpaper lies in the fact that silicate of soda adhesives develop a very decided increase in viscosity with a small decrease in their moisture content, whereas, in the case of gelatinized starch or starch derivative, adhesives, the increase in viscosity is relatively very small with a corresponding decrease in moisture content.

In the manufacture of corrugated board it is not necessary and often not possible that the adhesive bond be completely dry when the board comes oil the machine as the complete drying out can be accomplished later more conveniently when the board is in the lie. It is necessary, however, that .the board be bonded sufllciently to allow its being cut, scored and handled when it comes an themachine. This being the case and inasmuch as the time required to form a bond with any adhesive is the time necessary for the adhesive to develop sufllcient viscosity to hold the paper together at the points of contact, it can be readily seen that under the same conditions of spread, temperature and moisture absorption by the paper, the silicate of soda adhesive will always form a suiiicient degree of bond in less time than a gelatinized starch adhesive, for ex .ample. This is particularly true when the cost situation makes it necessary to use considerably more water in the starch adhesive than is used in the silicate of soda adhesive. As a result,

gelatinised starch adhesives have never been able to successfully compete with silicate of soda from the standpoint of production speed when used on corrugatina machines making double faced corrugated board.

I have discovered that itispoasibleto'produce laminated products such as corruslted paper board,-usingthestarchadhesivediscloeedinmy copending application. supra. that are not only competitive from the standpoint of cost with the prior art products using silicate of soda as the bonding adhesive but in fact are oi a superior quality. Furthermore, the process of manufactureottheboardusingthlsstarchadhesivels characterisedby agreaterspeedotbondformation than the prior art process using silicate of soda. As a speciilc example, the machines for manufacturing my new corrugated paper board. when using my new adhesive. may be operated from ten to twenty per cent faster than would be otherwise possible.

The laminated paper board of my invention does not cause discoloration, staining or tarnishingofthematerialswrappedorenclosedinthis board particularly because of the fact that the bonding agent used for unltlns the several plies oftheboardhasanextremelylowalkalinitycharacteristic.

An object of my invention is to provide a new and improved type of laminated product such as corrugated paper board that is superior to the laminated products produced with silicate of soda adhesive and that can be manufactured with substantially greater speed and less cost.

I have discovered that a superior laminated agent for the several laminations ungelatinised starch in conjunction with a suitable carrier or suspension medium. I have also found that the final characteristics of the board are somewhat dependent upon the balance or relationship between the ungelatinized starch. as the potential adhesive, and the carrier or suspension medium. While it is true that the adhesive disclosed and claimed in my copending application, supra. may be used for various purposes other thanlaminated products, the corrugated paper board and like products of the present invention are largely dependent for their superior characteristics upon the use oi this adhesive. The salient features of this adhesive and its pertinency to the present invention are discussed below.

This adhesive, which I use as the bonding'agent for my laminated products, diners from silicate of soda or a gelatinized type of starch adhesive in its bonding function. In my laminating opera-' of the adhesive mixture is raised to such an ex-' tent that an immediate bond is formed. Because of the great extent to which the viscosity can be increased by this method, it is possible to use from three to five parts of water to one part of dry material in my type of adhesive and still obtain a sumcient viscosity increase upon the appligelatinise very rapidly so that it will develop a highdegreeofviscosityinashortlengthoftime.

This factor will determine the rate of speed at 20 which the paper can be bonded on the machine.

It is desirable that this starch have a fairly low temperature of gelatinisation in order that it will be within the temperature range developed on the machine. This factor will also determine 25 thespeed atwhich'thepapercanbebondedon the machine.

It is desirable that this starch develop a high degree oi viscosity on gelatinising because this factor will largely determine the amount of wa- ,9

terthatcanbe used in the adhesiveformula. The

greater the viscosity developed. the larger the .amountof water thatmaybeused,whichwilireducethe cost. Also. the greater the viscosi y. the

greater the strength of the bond which holds the 35 paper together when it comes oi! the machine. The balance between these factors depends on the type or operation and type of laminated product desired by the user.

It is desirable that the starch upon selatinisationformatackyorstickygelasthistendsto insure against breakage of the newly formed bond when the board is handled soon after coming'oi! of the machine.

In regard to the portion of my adhesive which forms the carrier or suspension medium for the ungelatiniaed starch portion. it is desirable that this materialbeofsuchanaturethatitmaybe prepared with water to form a free flowing solution or colloidal solution of sumcient viscosity to hold the granules of ungelatinised-starch in suspension. and also enable the adhesive to be picked up by the rolls of the machine and applied to the paper.

The more essential features desired in a carrier for my purpose are as follows:--

1. It should hold the ungelatinized starch portion of the adhesive in a state oi suspension and thus prevent'any undue separation or settling out of the llnlelatlnized starch granules.

2. It should pick up evenly and well on the smooth rolls of a corrugating machine. for example, and act as a medium for transferring the adhesive to the paper to be bonded.

3. It should be of suihcient viscosity to enable the adhesivetostanduponthesurfaceofthe paper after it has been applied and yet it should be of such a nature that it will eflectively wet the. paper sin-faces to be bounded;

4. It should not cause the adhesive to foam in the glue boxes of the machine.

5. It should be capable of imparting sumcient viscosity to the adhesive to enable it to function properly even when, for example. from two to seven parts of water are used.

The carrier or suspension medium has beenl5 referred to as gelatinous or as having gelatinous characteristics. 1 have used these terms in their more popular sense to indicate the viscous hydrogel or hydrosol carrier medium of my invention as contrasted with-those other mediums which with relatively small amoimts of water produce viscous solutions. I have clearly indicated the characteristic desired in my carrier. Thus, I do not wish to be limited by my terminolcgy in this connection to a strictly gelatinous substance. It will be noted, for example, that I have proposed to use hydrosol carriers such as dextrins, starch gums and vegetable gums, as well as hydrogel carriers such as gelatinized starch. In the use of the terms gelatinous I intend to include all such types of substances having the desired characteristics whether or not they contain additional components as in the case of certain types of flours and irrespective of any preliminary treatments to which they may have been previously subjected. I The use of the terms ungelatinized starch or ungelatinized amylaceous material I intend to include all substances containing such ungelatinized starchy component or components capable of taking up water upon being subjected to heat, irrespective of any preliminary treatment such as partial gelatinization or conversion. It is only necessary that there be such a proportion of ungelatinized starchy components present in my potential adhesive as to provide the necessary effective increase in viscosity upon the application of heat in situ to form an effective bond. For example, certain ungelatinized starch gums might ordinarily be considered as a converted material. However, the ungelatinized starchy components present in such gums are available and eflfective to give the desired bonding action in situ as described in th s specification. i The formulasfor several adhesives that I have .found in practice to be very satisfactory as bondin: agents for my laminated products and par- "ticularly for the corrugated board manufactured with the present types of corrugating ma- ,chines, are.as follows:

5 The carrier 'portion' oi the adhesive is pre- 45 lbs. or this blend is mixed with 168 lbs. of cold for 1 a period of about 30 minutes.

Duringthismixingperlodthestarchinthemixture is gelatinized by the caustic soda formed by the reaction between the soda ashand lime. Subsequently, this gelatinized starch is acted on by the barium peroxide which thins it out to a smooth fluid consistency. At the end of this time, 1 pint of formaldehyde is added to the mixture to stop any further action of the barium peroxide and the mixture is diluted with an additional 400 lbs. of water. Other aldehydes as well as sulphurous acid, bisulphites or other suitable reducing agents may be substituted for the formaldehyde.

The imgelatinized potentially adhesive base portion of the adhesive contains the following:

Pounds Tapieca flour Bor 3 water 184 These three materials are mixed in a separate container and then added to the carrier, prepared Formula #2 The carrier portion of the adhesive is prepared as follows:

Blend Per cent Tapioca flour 45 Soda ash 20 Calcium hydrate 15 Barium peroxide V2 Clay (300 mesh) 19 /2 45 lbs. of this blend is mixed with 168 lbs. of cold water for a period of about 30 minutes. During this mixing period the starch in the mixture is gelatinized by the caustic soda which is formed and is subsequently acted on by the barium peroxide, which thins it out to a smooth fluid consistency. At the end of this time, 1 pint of formaldehyde is added and the mixture diluted with an additional 400 lbs. of water.

The ungelatinized potentially adhesive base portion of the adhesive contains the following:

Pounds Cornstar h 140 Bor 3 Water 184 These three materials are mixed in a separate container and then mixed with the carrier." The resulting mixture containing the gelatinized carrier and ungeiatinized base is then agitated for about 30 minutes, after which it is ready for use on the machine.

The above formula is similar to Formula #1, with the exception that instead of tapioca flour, corn starch is used for the ungelatinized starch portion of the adhesive. The amount of soda ash and lime is increased over that used in Formula #1 so as to form a larger amount of caustic soda and thus lower the gelatinization temperature of the corn starch and increase its speed of gelat- Jaisaticn. 'fhis formula also has'been 'ps'ovai commercially satisfactory by actual operation on mercial operation.

5 .Inbothoftheexamplesmentionedabove,soda

ashandlimeareused asaconvenientmeansoi' introducing caustic soda into the formula. 'Ihe eausticsodathus formednotonlyactsasameans ofgelatinisingthestarchinthecarrier,butalso losubsequentlyactaasameansofloweringthe gelsltinixation, temperature and increasing the gelatinisation speed of the ungelatinised starch portionofthe adhesive whenthebondisformed on the machine.

ll The barium peroxide when used with sodaash is aninert filler which is not essential to the success of the adhesive. It is used in this particular case merely to prevent undue lump l up of the carrier mixture when it is added to the water.

The borax used in the formula performs the function of increasing the degree of viscosity developed by the adhesive on the machine and thus enables the use of the large amounts of water specified in the above formulae.

Assn alternativeto theuseofboraxasa vis- 35 codty increasing agent in developing the adhesive bond in situ sodium aluminate as well as other soluble borates and aluminates can be used.

Several other examples of adhesiversuitable for use in my corrugated board and other lami- 4 nated products are as follows:

Formula #3 Per t Blend cen Corn star 08.5

45 Calcium hydrate 4.5 Boda ash 0.0 Barium per 1.0

60 Corn starch .lbs- 160 Sulphonated castor oil pint.. 1 Borax lbs..- 2 Water 113.. 190

These four materials are mixed in a separate container and then mixed with the carrier. The resulting mixture containing the gelatiniaed carrier and ungelatinized base is then agitated for about so minutes, after which it is ready for use on the machine. In this formula, a modified gelat- 7 iniaedcornstarchisusedasthecarriermedium and corn starch is also used for the ungelatinised portion of the adhesive.

' other of the various water soluble sulphonated oils, alcohols, soaps or fatty substances effective 76 as wetting agents can be used to improve the a,os1,oas I mild #4 80 lbs. of partially dextrinised starch are cooked with 250 lbs. of water to a temperature of 190 10 1".andthencooledtoatemperatureofbelow 100 1". In aseparate container, 100 lbs. of tapioca. rye orpotatostarcharcmixedwithm lbs. ofwaterandaddedtotheabovemixture. Thematerlal is then mixed until homogeneom, after which ll it is ready to run on the machine.

An adhesive formula of this type is of advantage whenanadhesiveisdesiredwhichmust be free from alkaline substances. In this specific instanceacookedpartialiydextrinisedstarchis used as the carrier medium. The degree of dextrinisationshouldbesuchthatthcfinalviscosity of the adhesive when mixed up is about thesameasthatofta' toQOBJiilcateofsoda. Either tapioca, rye, or potato starches or blends 95 arespecifiedfortheungelatinisedstarchinthis non-alkaline formula because they gelatinire rapidlyenoughtoenabletheadhesivetobeused satisfactorily on the machines without the necessity of adding caustic'soda to further increase the speed of gelatinization.

Ifitisdesiredtousecornstarch'inaformula of the non-alkaline type, it is usually onhigh speedmachinesto addsumcient amounts of such chemicals as: zinc chloride, calcium chloride, urea, formaldehyde, etc., which are nonalkaline and yet have the property of lowering the gelatinization temperature of starches, in order to bring the setting time of the adhesive within the speed range of the machine. 40

The above formulae for adhesives, which are suitable as bonding agents for my laminated prodnets, are merely specific examples of those that I have found to be satisfactory in actual practice. Therefore, I do notintend to limit my invention to in laminated products to the use of these specific adhesives for various modifications and substitutions may be made in them without departing from my invention.

I appreciate that the Duerden Patent No. 820,756 issued in 1899 discloses a process for manufacturing a corrugated paper board using a starch and water suspension as the adhesive material which is converted into a bonding agent upon the application of heat. However, this patent fails to appreciate the necessity for the use of a "carrier with the starch to obtain a successfully operative process. In accordance with my present invention, I have developed. for the first time,

a commercially successful laminating process so using an amylaceous type adhesive as the bonding agent. As contrastedwith Duerden my invention includes the novel combination of a potentially adhesive ungelatiniaed amylaceous material and a hydrosol or hydrogel carrier sufii- 05 cientiy viscous to prevent undue settling out of the ungelatinized starch component and to prevent undue absorption of the adhesive by the paper. This combination provides for a' rapid formation of an effective bond during the lami- 7o hating process.

I have already noted some of the advantages to be obtained in the manufacture of laminated products when using as the bonding adhesive my novel combination of starch with a viscous caraosacas 5 tier, for example, the increased speed of bonding operation possible; the even distribution of the starch by preventing settling and separation ofthestarch; theevenandsuretransferofthe 5 adhesive to the surface to be bonded; the ability of the adhesivetostandontheuirfacetocompensate for uneven positioning of the surfaces: the characteristic of wetting the surface to obtain a sure bond without such absorption as to 10 result in a starved joint or bond; and the characteristic of carrying suilicient water to make the final cost attractive commercially while retain-.

ing a viscosity and other characteristics to give a successful operation and bond. There are 16 other advantages and properties of my adhesive and operation which will become apparent to those skilled in this art.

I have found that the temperature of gelatinisation of the ungelatinised starch portion of 2 the adhesive used in my laminated products may be lowered if dmired and the speed of gelatinization increased. Such lowering of the gelatinlzation temperature might be desired, for example,

if the natural gelatinization point of a given 2 starch were above the temperature acquired by the paper surfaces and bonding adhesive passing through the laminating machine. Also, it might be found desirable to make more certain that all the ungelatinlzed starch component becomes 30 gelatinizedduring passage in order to bring the setting time of the adhesive within the speed of the machine. This lowering of the gelatinization point and increasing the rate of gelatinization.

may also be desired for the purpose of increas- 35 ing the rate at which the paper surfaces can be processed, for an increase in rate of passage would normally result in a lower temperature at the bond. I have found in this connection that caustic soda or calcium hydrate and soda ash or 40 equivalent hydroxy compounds of the alkali and alkaline earth metals, capable upon reaction to form gelatinizing agents or zinc chloride, calcium chloride, urea, and formaldehyde, when mixed with my adhesive in proportions insumcient to 45 completely gelatinize the ungelatinized starch present, act to lower the gelatinization point or temperature of the ungelatinized starch and increase the rate of gelatinization for the purpose referred to above. so The proportion of carrier material and melatinizedstarchbaseintheadhesiveusedinmy laminated products may be varied through a fairly wide range while still obtaining satisfactory results. For example, a satisfactory ad- 55 hesiveofthis'typecanbemadeupwithaslittle as 15% ungelatinized starch and as much as 85% carrier material on a dry basis. if the amount ofwaterusedinthe formula islimitedtoless than2$partsofwatertolpartofthetotal .9 dry materials used. In general, the smallest proportion of ungelatinlsed starch that can be used in an adhesive composition for my purposes is that amount which upon complete gelatinization after being subjected to heat in passage through the fabricating machine will give an apparent and usable increase in viscosity resulting in an immediate adhesive or bonding action. The greatest proportion of ungelatinized starchthatcanbeusedintheadhesivecomposi- .material fl.

intoconslderationallofthefactorsofmyadhesive already enumerated.

' It is necessary that the viscomty developed by this adhesive composition when it is completely gelatinised on the machine be suiiicient to hold 5 the paper plies together when they come off the machine so they may be .cut and handled as a unit without breakage of the bond. It is this factor which determines the greatest proportion of water that can be used in the adhesive composition which serves as the bonding agent for my new laminated products.

One illustrative embodiment of my invention in laminated products and particularly as applied to 'the manufacture of corrugated paper board is described below and illustrated in the accompanying drawing in which:

Figure l is a diagrammatic representation of I a system of making corrugated paper board in which the several paper plies are bonded together by means of the special type of starch adhesive described above, and

Figure 2 is a perspective view of a laminated corrugated paper board made in accordance with my invention, the top layer of paper being 26 partially separated from the inner core to illustrate the method of uniting.

Referring now to Figure l, the various mecha nisms of .this system have been illustrated entirely in diatic form since they are not, 30 per se, a part of this invention. My invention may be carried out by means of various other types of machinery than that illustrated in Figure 1 and furthermore. it is not limited to the manufacture of the specific type of corrugated paper board shown in Figure 2 but may be applied to the manufacture of numerous other types of laminated products, made by similar methods. However. the following description of the operation of the system in Figure 1 will serve :10 illustrate one specific application of my inven- The paper, which is to form the core of the corrugated paper board made in the system shown in Figure 1, is stored upon the supply roll II. During operation, this paper is unwound from the roll II and passes between steam jets II, which emit a fiow of steam for moistening and softening the strip of paper i2. After passing through the steam jets H, the strip l2 passes over the guide roll I! and thence between the two corrugated rolls It and 15, which rotate in such a manner that the strip of paper I! is crimped or folded into substantially rectangularly shaped portions.

After leaving, the corrugated roll ii, the corrugated strip of paper "a, passes on to the much larger roll I, which for clearness of illustration is shown as a smooth surface roll but may be corrugated if desired, and there comes into contact with the adhesive supplying roll II. This roll I1 is caused to rotate and is supplied with one of the carbohydrate ungelatinized types of adhesive materials, such as those described hereinbefore, by means of the roll It, which is suspended in the container I! filled with the adhesive The adhesive covered roll I! causes a coating of the adhesive tape applied to the convex portions on one side of the corrugated strip of paper "a passing around the periphery of the roll it. A little further around the roll ll, the corrugated paper lia comes in contact with another strip of paper 26, which'is to form one of the liners in the final product. This strip of paper 20 is supplied from supply roll II, and

is brought into contact with the corrugated strip otpaper ilabymeansoftheguideandtenaion rolls 2!, I3, 24 and 2'. The roll 2! cause the stripofpaperfltocomeintointimatecontaet withthecoatedportionsofthecornigatedstrip ofpaper llaontheroll ",sothatthetwostrips arecausedtobeunited. Theroll itispreferablyheatedbymeansoisteamforthepurpose of drying the steam-moistened paper Ila and for eausingtheadhesivetounitethelinerstripli to the corrugated coil "a.

The corrugated strip "6 and the liner 2. united thereto now pass around the roll 21 in such a manner that the uncoated side of the corrugated strip lie is brought into contact with a second adhesive supply roll II. This roll is caused to rotate and is supplied withadhesive material by means of the roll I! suspended in the container 80. which is filled with the ungelatinized adhesive material ii. The roll 18 applies a coating of my adhesive material to the convex portions of one side of the corrugated strip liointhesamemannerastheilrstadhesivesupplying roll il coated the reverse side of this corrugated strip. As the corrugated strip a, which now has a liner 2' united to one of its surfaces and has an adhesive coating deposited on the ridges of its other surface, leaves the roll 21, it comes into contact with the strip of paper I! which is to form the other liner. This strip of paper If is supplied from the supply roll If and is brought into contact with the coated side of the corrugated strip Ila by means of the guide and tension rolls 34, II, 80 and 81.

After leaving the roll 31, the assembly, comprising the inner corrugated strip of paper Ila, a top liner I2 and a bottom liner 2! passes between the hot plate II and the brushes 3!. The heat from the hot plate It is for the purpose of converting the ungelatinized portion of the adhesive material, which has been previously deposited between the core and the outside liners, to a geiatinized state. This heat treatment so modii'ies the starch adhesive that the viscosity is increased to a point where it becomes eflective as a bonding agent and partially dries it. The brushes to serve the purpose of keeping the paper board assembly in slight contact with the hot plate II during the time of heating.

The rubber covered rolls serve to pull the three strips of paper its, II and 82, through the entire system. The iinished paper board, leaving the mils ll, is cut to any desired length by means of the cutters ii.

The hot plate ll shown in Figure l, is operated at a temperature of approximately 250 1". to 875 1''. The paper board is fed past the hot plate at a rapid rate. which, depending upon the kind of paper being used and also production requirements, varies between 175 to-325 feet per minute. Even at the top speed of 325 feet per minute, the originally ungelatinised adhesive material of my invention will be converted to a geiatinized form and set to form a strong bond between the several pieces of paper of which the board is made.

Referring now to Figure 2. a piece of paper boardofthetypemadeinthesystemofrigure 1 is illustrated. This board comprises a corrugated inner core 42 and two liners 43 and 44. These linersareflrmlyunitedtothecorebymeansof the geiatinized adhesive material, converted to that form in situ, a portion of which is shown at 48. The carrier portion of my adhesive acts insomeeasestosizethepaperatthebond, thus forming a better base on each paper surface for the bonding agent. when the adhesive 45 is one of the types which I have described above, and is used for uniting the originally separate pieces of paper in accordance with the method described above in connection with Figure l, the board will possess the advantages and improvements outlined h'ereinabove as characteristic of my invention and will be void of the disadvantages and limitations of the prior types of paper board to which reference has previously been made.

While I have described only a specific form of product and operation, these are to be considered merely as illustrative of my invention. For example. the potential adhesive may be applied to a liner in narrow spaced applications and the operation so synchronized as to bring the corrugated tips of the core into contact with such applications. Other modifications and improvements within the scope of my invention will probably become apparent to those skilled in this art. The appended claims indicate some of the novel features of my invention.

I claim:

l. The process of continuously forming a corrugated paper board having a corrugated core and at least one paper liner attached thereto which includes the steps of continuously applying to the tips of the corrugations a potential adhesive comprising a mixture of ungelatinized starch and a gelatinous aqueous carrier medium of such viscous nature as to carry said ungelatinized starch in a state of relatively permanent and uniform suspension and to permit the retention oi said viscous mixture on the tips substantially as applied without material absorption of the aqueous content by the paper, bringing said corrugated core and applied potential adhesive continuously into contact with a liner to form an assembly and continuously passing said assembly with its potential adhesive through a heating zone whereby sumcient of the ungelatinlzed starch component is geiatinized to thereby render the potential adhesive effective to give an immediate adhesive bond for uniting said liner and corrugated core.

2. The process of continuously forming a corrugated paper board having a corrugated core and at least one paper liner attached thereto which includes the steps of continuously applying to the tips of the corrugations a potential adhesive comprising a mixture of ungelatinized starch and a geiatinized starch carrier medium of such viscous nature as to carry said ungelatinized starch in a state oi relatively permanent and uniform suspension and to permit the retention of said viscous mixture on the tips substantially as applied without material absorption by the pape bringins said corrugated core and applied potential adhesive continuously into contact .with a liner to form an assembly and continuously passing said assembly with its potential adhesive through a heating'zone whereby sufllcient of the ungelatinized starch component is geiatinized to thereby render the potential adhesive eil'ective to give an immediate adhesive bond for uniting said liner and corrugated core.

3. The process of continuously forming a corrugated paper board having a corrugated core and at least one paper liner attached thereto which includes the steps of continuously applying to the tips of the corrugations a potential adhesive comprising a mixture of ungelatinized starch and a vegetable gum gelatinous aqueous carrier medium of such viscous nature as to carry substantially as applied without material absorption by the paper, bringing said corrugated core and applied potential adhesive continuously into contact with a liner to form an assembly and continuously passing said assembly with its potential adhesive through a heating zone whereby sumcient of the imgelatinized starch component is gelatinized to thereby render effective the potential adhesive to give an immediate adhesive bond for uniting said liner and corrugated core.

4. The procem of continuously forming a corrugated paper board having a corrugated core and at least one paper liner attached thereto which includes the steps of continuously applying to-the tips of the corrugations a potential adhesive comprising a mixture of ungelatinized starch and a gelatinous aqueous carrier medium comprising clay and of such viscous nature as to carry said ungelatinized starch in a state of relatively permanent and uniform suspension and to permit the retention of said viscous mixture on the tips substantially as applied without material absorption by the paper, bringing said corrugated core and applied potential adhesive continuously into contact with a liner to form an assembly and passing said assembly with its potential adhesive through a heating zone whereby suilicient of the ungelatinized starch component is gelatinized to thereby render the potential adhesive effective to give an immediate adhesive bond for-uniting said liner and corrugated core.

5. The process of continuously forming a corrugated paper board comprising a corrugated core and a paper liner attached thereto which includes the steps of continuously applying to the tips of the corrugations a potential adhesive mixture comprising ungelatinized starch having the property of taking up water upon the application of heat, said starch being suspended in a gelatinous water-containing viscous carrier medium, bringing said corrugated core and applied potential adhesive continuously into contact with a liner to form an assembly and continuously passing said assembly with its potential adhesive through a heating zone whereby the suspended ungelatinized starch takes up water from said carrier, the amount of water present in said carrier being such that the suspended starch takes up a sufllcient amount of the same to allow substantially complete gelatinization and to cause an immediate and eiiective increase in viscosity of said mixture within said heating zone resulting in an adhesive bond for uniting said liner corrugated core.

6. The process of continuously forming a corrugated paper board assembly comprising a corrugated paper core and a paper liner attached thereto which process includes the steps of continuously applying to one paper portion of said assembly a potential adhesive in a series of spaced relatively narrow applications, said potential adhesive mixture comprising ungelatinized amylaceous material having the property of taking up water upon the application of heat suspended in a gelatinous, water-containing, viscous carrier medium, bringing said paper portion with the applied potential adhesive continuously into contact with the other paper portion to form an assembly and continuously passing said assembly with its potential adhesive through a heating zone whereby the suspended ungelatinized amylaceous material takes up water from said carrier,

gelatinized amylaceous material will cause an immediate and effective increme in viscosity of said mixture resulting in an adhesive bond for uniting said linenand corrugated core. j

"I. The process of continuously forming a corrugated board assembly comprising a corrugated paper core ands paper liner attached thereto which process includes the steps of continuously applying to one paper portion of said assembly a potential adhesive in a series of spaced relatively narrow applications, said potential adhesive comprising a mixture of ungelatinized amylaceous material capable of taking up water upon the application of heat and a gelatinous aqueous carrier medium of such viscous nature as to carry said ungelatinized amylaceous material in suspension and to Permit the retention of said viscous mixture substantially as' applied without material spreading and without material absorption of the aqueous content by the paper, bringing said paper portion with the applied potential adhesive continuously into contact with the other paper portion to form an assembly and continuously passing said assembly with the applications of potential adhesive in contact with the assembled paper through a heating zone whereby sulficient ungelatinized amylaceous material is gelatinized to increase the viscosity to give an immediate and effective adhesive bond for uniting said assembly.

8. The process of continuously forming a corrugated board assembly comprising a corrugated paper core and apaper liner attached theretowhich process includes the steps of continuously applying to at least one paper portion of said assembly a potential adhesive in a series of spaced relatively narrow applications, said potential adhesive comprising a mixture of ungelatinized amylaceous material capable of taking up water upon the application of heat and a gelatinous aqueous carrier medium comprising a substance selected from the group consisting of gelatinized starches, dextrins and starchy gums, said carrier having such a viscous nature as to carry said ungelatinized amylaceous material in suspension and to permit the retention of said viscous mixture substantially as applied without material spreading and without material absorption of the aqueous content by the paper, bringing said paper portion with the applied potential adhesive continuously into contact with the other paper portion to form an assembly and continuously passing said assembly with the applications of potential adhesive in contact with the assembled paper through a heating zone whereby suillcient ungelatinized amylaceous material is gelatinized to increase the viscosity to give an immediate and eifective adhesive bond for uniting said assembly.

9. The process of continuously forming a corrugated paper board having a corrugated core and at least one paper liner attached thereto which includes the steps of continuously applying to the tips of the corrugations a potential adhesive comprising a mixture of ungelatinized amylaceous material and a gelatinous aqueous carrier medium of such viscous nature as to carry said ungelatinized amylaceous material in a state of relatively uniform suspension and to permit the retention of said viscous mixture on the tips sub-.

'stantiaily as applied without material absorpitionhythepapeabringingsaideonugatedcore and applied potential adhesive continuously into contactwithaliner-toiorrnanassernblyaultlconviscouscarriermedium.andanagent iorincreas-' 'ingthe viscosityoitheungelatinisedstarehupon gelatinisation selected irom the group comisting oi soluble borates and aluminatu, bringing the paper portion with the applied potential adhesive continuously into contact with the other v v portiontoiormanassemhlyandpassing said assembly continuously with its potential adhesive through a heating sone whereby ungelatinised amylaceous material is gelatinised in situ in the presence oi a substance selected iron the groupconsistingoiaolubleboratesandaluminatesandtakesupwaterirom said carrier,tbe amolmt oi water present in said carrier being sumcient to allow said ungelatinised amylaceom material to become substantially "istinised within said heating none, the amount oi water present insaidcarrierbeingpresentinsuchasmall proportion that the amount taken up by said ungeiatinised amylaceous material will cause an immediateincreaseinviscosityoisaidmixtm'eresulting in an adhesive bond ior uniting said liner and corrugated core.

11. The process of continuously iorming a corrugated paper board assembly comprising a corrugated paper core and a paper liner attached thereto which process includes the steps of continuously applying to one paper portion oi said assembly a potential adhesive in a series oi spaced relatively narrow applications. said potential adhesive mixture comprising imgelatinized amylaceous material. a soluble borate and a gelatinous aqueous carrier medium. said carrier medimnbeingoisuehviscousnature astocarrysaid ungelatini aed starch in a state of relatively permanent and uniiorm suspension and to permit .the retention oi said viscous mixture substanvportion to iorm an assembly and continuously passing said assembly with its potential adhesive through a heating acne whereby suiiicient oi the ungelatiniaed starch component is gelatinised in the presence oi the soluble borate to thereby render the potential adhesive eiiective to give an immediate adhesive bond ior uniting said liner and 15 corrugated core.

12. A process oi continuously iorming a corrugated paper board assembly comprising a corrugatedpaper core and a paper liner attached there- .to,whichprocess includes the steps of continuously applying to one paper portion oi said assembly a potential adhesive in a series of spaced relatively narrow applications, said potential adhesive mixture comprising ungelatinised amylaceous material having the property oi taking up water upon substantially gelatinized within said heating zone,

the amount oi water present in said carrier being present in such a small proportion that the amount taken up by said ungelatinized amylaceous material will cause an immediate increase in viscosity oi said mixture resulting in an adhesive bond for uniting said liner and corrugated core. a

18. In a process as defined in claim 6 the preliminary operation consisting oi treating said ungelatinised amylaceous material with an amount of starch gelatinizing agent suiiicient to'lower the temperature at which gelatinisation takes place in situ within said heating none but insuiiicient to cause gelatinizatlon prior to the heating with-' in said heating sone. e

' JORDAN V. BAUER. 

